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View Full Version : Looking for the definitive answer on Thermostat for LT1


flya750
05-11-2012, 04:56 PM
My dealership is telling me they recommend using a 160 in place of the stock 143 for the lower thermostat.

So in essence they recommend for me to install two new 160's instead of the 160 and the 143 that the boat came with.

They claim it will help make my heater work better.

What do you all think?

BTW... The water pump in my 1997 LT1 was worn out after 800 hrs.. Makes me wonder how many boats out there are running with water pumps on their last legs...

Jerseydave
05-11-2012, 05:02 PM
This thread answer all of your questions about LT-1 t-stats and getting more heat for the heater.

http://mastercraft.com/teamtalk/showthread.php?t=31626&highlight=overheating

The 143 lower t-stat and 160 upper t-stat are the only way to go. Don't use automotive t-stats either, you would be asking for trouble.

flya750
05-11-2012, 07:43 PM
HMMMMM.. I read that link you posted JerseyDave and it seems to me that consensus is to use a 160 in place of the 143.

I talked with my dealer again tonight and they mentioned that even Indmar recommends using a 160 thermostat if the LT1 has a heater.

One thing mentioned in that thread..."The 143 is the stat in the triangular "mixing" housing. It's job is to take motor warmed water and mix it with cold lake water, so there isn't so much of a thermal shock at the block's thermostat. The thermostat for the motor is under the aircleaner, under the filler neck. It should be 160 degrees. They used Robertshaw brand stock, I like Stants. That's the one that I got a custom 170 made, and it works great.

If your motor is running 143, that's too cold. The tolerances and clearances between components were designed for a higher temp, so everything has to thermal expand to fit right. That's the whole point behind "warming up" an engine. Plus will never burn off moisture and diluted fuel. "

Table Rocker
05-11-2012, 08:20 PM
flya750, if you haven't already ordered your water pump, you might get the one that has the heater-out port on the front. That will be the biggest help to having a hot heater.

The 93-96 Corvette water pump (AC Delco 251-554) (http://www.amazon.com/ACDelco-251-554-Water-Pump/dp/B000C9LS5K) has the proper port. You would need to add an inline valve to shut it off.

The stock location is the spigot on top of the mixer and uses mixed water to the heater. If the engine thermostat is closed, it isn't getting hot water to the mixer. You can see how it wouldn't work very well.

I drilled and tapped a hole in my stock water pump. Now water flows directly out of the block and into the heater hose.
http://img194.imageshack.us/img194/251/img2398ej.jpg

flya750
05-11-2012, 09:38 PM
I did already buy my water pump. There is a mod talked about on the link above that uses a T junction where the heat sensor goes. The mod calls for that to feed the heater and for the return to go back into the pump up by the top.

I'm considering getting a T junction for my heat sensor...

Table Rocker
05-11-2012, 09:51 PM
I didn't already buy my water pump. There is a mod talked about on the link above that uses a T junction where the heat sensor goes. The mod calls for that to feed the heater and for the return to go back into the pump up by the top.

I'm considering getting a T junction for my heat sensor...If you get the 251-554 pump, you won't have to buy a tee and a hose barb. Also your temp sensor will still have water flowing past it when the heater is off. Look at the pic of the tee and see how far out of the water pump the sensor is. You will have to install an inline valve either way.

flya750
05-11-2012, 10:06 PM
If you get the 251-554 pump, you wont have to buy a tee and a hose barb. Also your temp sensor will still have water flowing past it when the heater is off. Look at the pic of the tee and see how far out of the water pump the sensor is. You will have to install an inline valve either way.

I already bought the pump... bummer...

Thanks for the Info Rocker!

ricford
05-11-2012, 10:14 PM
BTW... The water pump in my 1997 LT1 was worn out after 800 hrs.. Makes me wonder how many boats out there are running with water pumps on their last legs...

My 1996 LT1 water pump went last year at only 350 hours. I think it has more to do with age then hours, especially since it sits all winter. In a vehicle it is always immersed in coolant which is much less corrosive than water.

flya750
05-11-2012, 10:21 PM
What I can do is take my pump to someone to drill and tap the hole... I haven't installed the new pump yet.. I was going to do it tonight. If this fixes my heater problem that would be a huge bonus.
I run some long rivers and @ idle the heater is worthless....

Table Rocker
05-11-2012, 10:35 PM
What I can do is take my pump to someone to drill and tap the whole... I haven't installed the new pump yet.. I was going to do it tonight. If this fixes my heater problem that would be a huge bonus.
I run some long rivers the @ idle the heater is worthless....Drilling and taping works great. You will have to buy some fittings.

I ended up using this valve right after the fitting on the pump, so I could shut it off.

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/$(KGrHqJHJCoE8fjPphjeBPNqycYC6w~~60_58.JPG (http://www.ebay.com/itm/250993788660?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_4628wt_1048)

flya750
05-11-2012, 11:04 PM
Back to the thermostats.... If I go with the drilling and tapping my water pump .. that should fix my heater and I can go with a 143 in the lower vs a 160. ??? Just like Stock...?

I'm not fully sure how this cooling system all works... but I'm learning...;)

Table Rocker
05-11-2012, 11:25 PM
Back to the thermostats.... If I go with the drilling and tapping my water pump .. that should fix my heater and I can go with a 143 in the lower vs a 160. ??? Just like Stock...?That is the way I see it.

flya750
05-12-2012, 12:00 PM
Hey Rocker,

How did you drill and tap a hole in the pump without getting metal shavings inside the pump?

flya750
05-12-2012, 12:47 PM
My 1996 LT1 water pump went last year at only 350 hours. I think it has more to do with age then hours, especially since it sits all winter. In a vehicle it is always immersed in coolant which is much less corrosive than water.

Yes, it makes you wonder why these pumps are not marinized in anyway..?????

I wonder if the new Ilmor motors have marinized water pumps.. if not what a scam on so many levels...These boat prices deserve a marinized water pump...

Table Rocker
05-12-2012, 01:07 PM
Hey Rocker,

How did you drill and tap a hole in the pump without getting metal shavings inside the pump?
I had the pump off when I did mine. I drilled and tapped and then blew it out with the air compressor. It is aluminum, so it taps very easily, but be careful tightening the fittings. It will strip easily too.